Foot-and-mouth disease, mad cow disease and bird flu, which have seriously affected the international economy in recent years, are typical biological invasions. 2 1 century, a series of epidemics began to wreak havoc around the world. The first is the outbreak of foot-and-mouth disease crisis. In 200 1 year, 2030 cases were found in Britain, during which more than 4 million livestock were slaughtered, and the government even used the army to participate in the slaughter and burial. In May 2005, Asian type I foot-and-mouth disease broke out in parts of Beijing, Shandong, Jiangsu and other places. The government promptly launched the emergency plan for foot-and-mouth disease prevention and control, blocked the epidemic area, culled livestock, strictly disinfected and strengthened epidemic monitoring, and the epidemic situation was effectively controlled. Just after the foot-and-mouth disease storm ended in 2002, Europe and even the whole world fell into the whirlpool of mad cow disease. Mad cow disease is a zoonotic disease. By February 2002, there were 1 14 cases of mad cow disease and 10 patients in the world. At present, the mortality rate of mad cow disease is 100%. Some experts believe that by 2020, there will be hundreds of thousands of mad cow disease patients, which may threaten the survival of mankind. From 2004 to 2005, human beings were frightened by avian influenza again. From July to June, 2005, 165438+ 10, more than1400,000 poultry were slaughtered or culled in the world, resulting in economic losses as high as $654,380 billion. The World Health Organization confirmed that 125 people were infected with avian influenza, and 64 of them died.
Apart from mad cow disease and foot-and-mouth disease, the disasters brought by pests at all times and in all countries are very painful. In the second half of the 5th century, the plague invaded the Middle East from Africa and then reached Europe, killing about 654.38 billion people. Measles, smallpox, bubonic plague and AIDS, which seriously affect human health, are the consequences of biological invasion. The cultivation of tropical rain forest areas by human beings has provided new opportunities for more viruses to invade, including viruses previously carried only in wild animals, which has caused many new African snail diseases to occur in humans, such as Ebola virus that attacked Congo and other places many years ago.
Biological invasion not only directly damages the living environment and health of people, animals and plants, but also damages the health of other species by releasing harmful substances. Ragweed and ragweed are native to North America and are now distributed in Northeast China, North China, East China, Central China and other provinces and cities 15. The pollen of ragweed is the main pathogen causing human pollen allergy, which is very harmful to people's health. It can cause allergic asthma, rhinitis and dermatitis. It recurs at the same time every year, and the condition is getting worse every year. In severe cases, emphysema, heart disease and even death will occur. This is "hay fever". Eupatorium adenophorum contains toxins that can easily cause asthma in horses and sheep.
Once the invasion is successful, exotic creatures will grow and breed rapidly in the local area, change the local ecological environment, endanger local production and life, and cause huge economic losses. It is extremely difficult to eradicate these invasive species completely, and it is also extremely expensive to control their harm and spread.
The ecological harm caused by biological invasion is mainly realized in the following three ways: 1. Competing with crops for niche will bring diseases, increase production costs, reduce crop yield and bring direct economic losses. For example, the yield loss caused by peanuts in the whole growth period of rice, wheat, corn, sweet potato and lettuce reached 45%, 36%, 65, 438+09%, 63% and 47% respectively. Liriomyza sativae is parasitic on 22 families 1 10 plants, especially vegetables and fruits. The damage area exceeds10 million square kilometers, and the annual cost of controlling Liriomyza sativae is 450 million yuan. Invasive pests such as pine wood nematode, slash pine, Hemiberlesia pitysophila and Hemiberlesia pitysophila affect about 6.5438+0.5 million square kilometers of forest every year. Invasive pests such as rice weevil, liriomyza sativae, potato beetle and African snail affect farmland140 ~1600,000 square kilometers every year. 2. Alien invasive species have changed the local habitat, brought a series of indirect economic losses and increased the ecological cost of society. For example, after the water hyacinth plant died, it was mixed with sediment and deposited on the bottom of the water, raising the riverbed, making many rivers, ponds and lakes gradually turn into swamps, and some of them were abandoned, which adversely changed the surrounding climate and natural landscape and aggravated the harm of drought and flood disasters; Moreover, water hyacinth plants absorb a lot of toxic substances such as heavy metals and sink to the bottom after death, which constitutes secondary pollution to water bodies. 3. controlling the evil consequences caused by the invasion requires a lot of economic expenditure. Reversing the damage caused by biological invasion and repairing its ecological damage require considerable economic support, which is a long-term process. In 1950s, a large number of introduced water hyacinths proliferated in China, which hindered shipping and seriously damaged the ecological balance of rivers. The annual salvage cost is as high as 5000- 10 billion yuan, resulting in economic losses of nearly 10 billion yuan.